public class Calculator {

	public static void main(String[] args) {
		 String[] testinputs = { \"( 10+2 )*(2+3)\", \"((1+2) - (1+2))\",
		 \"((1-1)/(2*2)) + 5\", \"5+5\", \"(1)\", \"3.5 - 1\" };

		for (String input : testinputs) {
			System.out.println(\"calculating \" + input);
			System.out.println(calculate(input));
			System.out.println(\"-----------\");
		}

	}

	private static double calculate(String input) {
		input = new String(removeSurroundingBrackets(input.toCharArray()));
		if (isNumber(input)) {
			return Double.parseDouble(input);
		}
		String[] parts = splitIntoParts(input);
		if (isNumber(parts[0]) && isNumber(parts[2])) {
			double result = operate(Double.parseDouble(parts[0]),
					Double.parseDouble(parts[2]), parts[1]);
			return result;
		}
		return operate(calculate(parts[0]), calculate(parts[2]), parts[1]);
	}

	private static double operate(double a, double b, String operator) {
		if (operator.equals(\"+\")) {
			return a + b;
		}
		if (operator.equals(\"-\")) {
			return a - b;
		}
		if (operator.equals(\"/\")) {
			return a / b;
		}
		if (operator.equals(\"*\")) {
			return a * b;
		}
		return 0;
	}

	private static boolean isNumber(String string) {
		try {
			Double.parseDouble(string);
		} catch (NumberFormatException e) {
			return false;
		}
		return true;
	}

	private static String[] splitIntoParts(String input) {
		StringBuilder[] parts = initParts();
		char[] in = input.toCharArray();
		int part = 0;
		int bracketsOpen = 0;

		for (int i = 0; i < in.length; i++) {
			char c = in[i];
			if (c == '(') {
				bracketsOpen++;
			} else if (c == ')') {
				bracketsOpen--;
			}

			if (!Character.isWhitespace(c)) {
				parts[part].append(c);

				if (bracketsOpen == 0 && !(i + 1 >= in.length)
						&& !(isNumberOrDot(c) && isNumberOrDot(in[i + 1]))) {
					part++;
				}
			}

		}

		String[] result = new String[parts.length];
		for (int i = 0; i < result.length; i++) {
			result[i] = parts[i].toString();
		}
		return result;
	}

	private static boolean isNumberOrDot(char c) {
		return Character.isDigit(c) || c == '.';
	}

	private static char[] removeSurroundingBrackets(char[] a) {
		if (a[0] == '(') {
			int openBrackets = 0;
			for (int i = 0; i < a.length; i++) {
				if (a[i] == '(') {
					openBrackets++;
				} else if (a[i] == ')') {
					openBrackets--;
				}
				if (openBrackets == 0 && (i == a.length - 1)) {
					char[] r = new char[a.length - 2];
					for (int j = 1; j < a.length - 1; j++) {
						r[j - 1] = a[j];
					}
					return r;
				} else if (openBrackets == 0) {
					break;
				}
			}
		}
		return a;
	}

	private static StringBuilder[] initParts() {
		StringBuilder[] parts = new StringBuilder[3];
		for (int i = 0; i < parts.length; i++) {
			parts[i] = new StringBuilder();
		}
		return parts;
	}

}

calculating (10+2)*(2+3)
60.0
-----------
calculating ((1+2) - (1+2))
0.0
-----------
calculating ((1-1)/(2*2)) + 5
5.0
-----------
calculating 5+5
10.0
-----------
calculating (1)
1.0
-----------
calculating 3.5 - 1
2.5
-----------

public static void main(String[] args) {
	System.out.println(\"type in 'quit' to leave the program\n\");
	while (true) {
		java.util.Scanner scan = new java.util.Scanner(System.in);
		System.out.println(\"Your input\");
		String input = scan.nextLine();
		if (input.equals(\"quit\")) {
			break;
		}
		try {
			double result = calculate(input);
			System.out.println(\"Result: \" + result + \"\n\");
		} catch (Exception e) {
			System.out.println(\"Your input was not correct\n\");
		}
	}
}

#!/usr/bin/python

print 'Press Ctrl&C to exit\n'

while True:
        x = input('Enter operation: ')
        print 'Result:', x

Press Ctrl&C to exit

Enter operation: 10+10
Result: 20
Enter operation: 20/10*2+1
Result: 5
Enter operation: (5*6)-(23/2)
Result: 19

#!/usr/bin/python
while True:
    op = raw_input(\"Enter operation: \")
    if op.find('+') != -1:
	sp = op.split('+')
    firstnumber = (sp)[0]
    secondnumber = (sp)[1]
    res = int(firstnumber)+int(secondnumber)
    print \"Result:\", res

Enter operation: 35+35
Result: 70

#!/usr/bin/perl

print \"Enter your equation: \";
$eq = <STDIN>;
print eval $eq;
$toMakeUserPressEnterToClose = <STDIN>;